Heat transfer between exothermic and endothermic reactions



June 16, 1953 N. L. mcKlNsoN 2,642,331 I HEAT TRANSFER BETWEENEXOTHERNIC AND'ENDOTHERMIC REACTIONS Filed Aug. 27, 1949 2 SheltS-Shllt1 NORMAN L. DICKINSON BY f 9'. HW

ATTORNEY June 16, 1953 N. L. DlcKlNsoN 2,642,381

' HEAT TRANSFER BETWEEN EXOTHERMIC AND ENDOTHERMIC REACTIONS flll ||2NORMAN L. DICKINSON y BY ' ATTORNEYS Patented June 1.6, 1953A .il a2,642,381

HEAT TRANSFER BETWEEN EXOTHERMIC AND ENDoTHERMIc REACTIONS Norman L.Dickinson, Basking Ridge, N. J., as-

signor to The M. W. Kellogg Company, Jersey City, N. J., a corporationof Delaware f Application'August 2v, 1949, serial No. 112,777

14 claims. (o1. 19e- 27) The invention relates to heat transfer betweenan exothermic reaction and an endothermic reaction. In one aspect theinvention relates to a method for transferring heat from a relativelylow temperature exothermic reaction to a relatively high temperatureendothermic reaction. In another aspect the invention relates to anintegrated process for treating hydrocarbon d1s- `tillate fractions byhydrodesulfurization and hydroforming.

There are numerous processes presently being operated or proposed whichtreat a feed stock by successive reactions such for example, as byhydrodesulfurization followed by hydroforming of a sulfur-containingVnaphthan fraction. In this example, the hydroforming reaction isendothermic, which reaction requires the addition of heat in order tomaintain substantially isothermal temperature conditions. Although' theprior hydrodesulfurization reaction is exothermic with the liberation ofa considerable amount of heat, the hydrodesulfurization reaction iselected at the same or lower temperature than the subsequenthydroforming reaction. This characteristic of the two reactionsprohibits direct heat exchange between the reaction Zones so as toutilize the exothermc heat of reaction of the hydrofluid externallyheated, or by the more usual manner of superheating the feed to thehydroforming step.` In general, it may be said that either of the abovemethods are undesirable in an integrated process since they do notutilize Lia) the exothermic heat of reaction liberated in the l sired,therefore, to provide a method for utiliz.

ing the exothermic heat of reaction of the hydrodesulfurization step inthe endothermic hydroforming step and also toprovide a method for atleast minimizing the temperature to `which the feed to the hydroformingstep must be preheated.

It is an object of this invention to provide a method for transferringheat from an exothermic reaction to an endothermic reaction in anintegrated process in which the exothermic reaction i is carried out ata temperature not higher than'` the temperature of the endothermicreaction.

Another object of this invention is to provide'V an improved method fortreating `a hydrocarbon'l distillate stock. l. Another objectof thisinvention is to provide an improved method for the hydrodesulfuriZa-f`tion and hydroforming of a distillate.

It is a further object of this invention to provide a process for theremovaly of nitrogen and sulfur compounds from a hydrocarbon distillate.

Still another object of this invention is to pro" Vide aV noveliiuidized type of operation for the:

hydrodesulfurization of a hydrocarbon distillate.

Another object of this invention is to provide a novel type of iiuidizedprocess for the hydroforming of a hydrocarbon distillate.

It is a further object of this invention to'pro`` vide a process forincreasing the catalyst life inv a hydrodesulfurization process and inahydroforming process. V

Various other objects and advantages will become apparent to thoseskilled in the art from the accompanying description and disclosure.

This invention applies specifically toV an integrated process involvingboth exothermic and endothermic reaction steps on a common feed stock,said steps being effected at substantially the same temperature, or oneof said steps being a relatively low temperature exothermic reaction andanother of said steps being a relatively high temperature endothermicreaction. According to this invention, exothermic heat is made .avail-Aable for the endothermic reaction by vaporizngV a liquid in indirectheat exchange with the exothermic reaction, compressing the vapors thusproduced, thereby increasing their temperature and raising theirtemperature of condensation, condensing the vapors thus compressed inindirect heat exchange with the endothermic reaction and returning theliquid thus condensed to The vinvention is adaptable to heat exchangebetween variy the system for repeating the cycle.

ous types of chemical reactions employing catalyst in'a stationary orfixed bed in which catalyst is contained in tubes surrounded by a heatexchange fluid, or in a uidized condition-or.. even in the absence of acatalyst. The inventionV has particular' applicability to a system inwhich reactant gasesare passed at a relatively highv velocity through areaction zone inthe presence' of finely-divided catalyst underconditions such that the catalyst vis suspended or entrained in thegaseous reaction mixture. The invention may be best understood by itsapplication to a specific in-iV tegrated process and the inventor haschosen for the description of this invention its application to anintegrated process involving the successive steps ofhydrodesulfurization and hydroforming of a sulfur-bearing hydrocarbondistillate. It is to be understood, however, that the invention haswider application to exothermic and endothermic reactions generally inwhich the exothermic heat is available at the same or lower temperturethan the endothermic recation. In the prooess to be described inconnection with the preferred application of the invention, numerousnovel features relative to specific steps of the hydrodesulfurizationreaction and the hydroforming reaction Will be discussed concurrentlywith the discussion of the heat transfer method of this invention.

The accompanying drawings are elevational views, partly in crosssection, diagrammatically illustrating a process and variousarrangements of apparatus suitable for carrying out the presentinvention. Figure 1 of the drawings is an arrangement of apparatus andflow diagram of an integrated process for the hydrodesulfurization andhydroforming of a hydrocarbon distillate fraction containing organicallycombined sulfur. In Figure l, a single heat exchange means is providedin each reaction Zone. Figure 2 represents a diagrammatic illustrationof a heat exchange system similar to that shown in Figure 1 except thatmultiple heat exchangers are employed in each of the reaction zones.Figure 3 diagrammatically illustrates a multi-stage hydrodesulfurizationreaction system with multi-stage heat exchange.

According to Figure l of the drawing, 10,000

barrels per stream day of a dehexanized California cracked naphtha ofthe following characteristics are treated:

.Table I Gravity, API 46.0 A. S. T. M. distillation:

I. B. P., F 217 330 348 373 395 E.P 426 Recov., percent 98.0

Residue 1.3 Loss 0.7 Aniline point, F 89 Octane number, CFRM 69.4 Reidvapor pressure,p.s.i 0.6 Sulfur, wt. percent 2.2

Nitrogen, wt. percent 0.20

Although Figure 1 is described with respect to a specific feed stock,the invention may be applied to the hydrodesulfurization of any straightrun or cracked naphtha containing from about 0.05 to about 5 weight percent sulfur and boiling within the range of about to about 600 F.Preferably, the feed stock to betreated in accordance with a process ofthe type shown in Figure 1 boils within the range of about 250 to about500 F. and has an A. P. I. gravity between about 40 and about 60G. Intreating such a feed stock according to the process to be hereinafterdescribed, 90 to about 100 per cent of the organic sulfur is convertedto hydrogen sulfide and removed.

The .aforesaid quantity of naphtha is introduced into the system throughconduit 4 and it is admixed with about 62,500,000 standard cubic feetper day of hydrogen-containing gas which includes 7,500,000 standardcubic feet of makeup hydrogen from conduit 6 and 55,000,000 standardcubic feet of hydrogen-containing recycle gas from conduit 31 or 5l. Themixture comprising hydrogen and naphtha is then passed through conduit 4to a lpreheater and vaporizer i which preheats the mixture to atemperature substantially equivalent to the desired hydrodesulfurizationtemperature which in this example is 850 F. The feed stock is pumped tothe desired pressure by a pump, not shown. Since the process of Figure 1involves both desulfurization and hydroforming and utilizes catalysttransfer between each of the aforesaid zones, it is preferred to effectboth reactions at substantially the samev pressure in order to minimizediniculties in the transfer of catalyst between zones. In the processillustrated, the pressure is 500 pounds per square inch gage.

From preheater l, the vaporized feed stock is passed through conduit 8to hydrodesulfurization reactor 9. Catalyst is introduced into transferline 8 through a conduit or standpipe 4l. This catalyst is afinely-divided solid material, the nature and composition of which willbe discussed more fully hereinafter. The catalyst is suspended in thereaction gases and passes by entrainment to reactor 9. In reactor 9, thenaphtha vapors pass upward through an elongated and enlarged reactionzone at a sufficiently high gas velocity that the catalyst particles aresuspended and continuously move in the direction of fiow of the gases inconcurrent flow. The velocity of the gases should be above about 5 feetper second and may be as 'high as 40 or 50 feet per second in order tomaintain the catalyst particles moving in the direction of ow of thegases and to prevent the formation of the conventional pseudo-liquiddense phase of catalyst particles characteri'zed by theinternal'circulation of catalyst particles from top to bottom of thedense phase. Normally, the higher the velocity the more uniform is theflow of catalyst and gases. Thus, the higher velocities are preferredfrom the standpoint of the physical condition of the reaction mixture.However, higher velocities require longer reaction chambers, and, from aconstruction standpoint, lower velocities within the above range arepreferable. The preferred velocities, taking into account both thephysical condition of the reaction mixture and the length of thereaction chamber, are between about 6 and about 15 feet per second.Employing such relatively high velocities, the catalyst is entra-ined ina highly dispersed condition in the gaseous reactants in reactor 9. Theconcentration of the contact material under such conditions of velocityand a suitableloading rate is between about l and about 20 pounds 'percubic foot. In comparison with the conventional pseudo-liquid densephase of finely-divided contact material, this concentration is one-halfor less of the density or concentration of catalyst in the dense phase,

At a space velocity of about 7 W./hr./w. (weight 0f naphtha per hour perweight of catalyst) and a reactor 3 feet 3 inches in inside diameter and80 feet in length, a gas velocity of about 6.8 feet per second and acatalyst concentration in reactor 9 of about25 pounds per. cubicfoot aresuitable for the operation to achieve the desired conversion. In theoperation shown in Figure 1, 90 to 100 per cent of the sulfur isconverted to hydrogen sulde, in the presence of a suitable catalyst.Nitrogenous organic compounds are also reduced to ammonia andhydrocarbons. The more reactive unsaturated compounds, such asmono-oleiins and dioleiins, are simultaneously hydrogenated to theircorresponding saturated compounds. In the particular reactionillustrated in Figure 1, about 16,700,00018. t. u.s per hour of heat arereleased at a substantially isothermal temperature of about 850 F.

An eiiluent comprising desulfurized naphtha, hydrogen sulde, hydrogen,relatively low boiling hydrocarbons and entrained catalyst is passedfrom reactor 9 through conduit II to separator I2. The effluentisintroduced through conduit Il tangentially into separator I2 to aid inthe separation of solid contact material from the reaction effluent. Acyclone separator (not shown) may be positioned within separator I2 toaid in removal of catalyst dust from the reacltion eiiluent. The cycloneseparator contains a dip leg projecting into the lower portion ofseparator I2. Contact material substantially at the temperature ofreactor 9 settles to thebottorn of separator I2 and passes through afunnel shaped bottom portion I3 .and through a standpipe or conduit I4into a stripping zone I5 which may contain bailes or the like. The levelof the catalyst bed in the stripping zone I5 is above the' lower end ofstandpipe I4 as indicated by numeral I1. Stripping gas is introducedinto the lower portion of stripper I5 through a conventional inletconduit and distribution means I8. Thev stripping gas along withstripped material is withdrawn from the upper portion of stripper l5through conduit I6 or may be passed directly into separator I2 by meansnot shown. The stripping gas removes tarry and carbonaceous deposits andoccluded gases from the catalyst and may also condition the catalyst. Asuitable stripping gas comprises any of the following: recycle gas,hydrogen, methane, carbon dioxide, steam, air, and nitrogen. Thestripped catalyst is withdrawn froml stripper l5 through conduit I9 andis passed to transfer line 39 of hydroforming reactorA 4I. In amodification of the invention, a portion or all of the catalyst may berecycled through conduit 20 to reactor 9. In general, it is preferableto recycle at least a portion of the stripped catalyst directly toreactor 9 in order to control the concentration of catalyst thereinindependent of catalyst circulation throughout the unit. The ratio ofrecycle catalyst to catalyst passed to reactor 4I is usually about 10:1.

The eiiluent from reactor 9, as previously dis# cussed, is removed fromthe'upper part of separator I2 and is substantially free from entrainedor suspended catalyst. However, in order to remove the last traces ofsuspended catalyst, this efliuent is passed through metallic lters (notshown) or other known means of dust recovery and then passed throughconduit 2|, condenser 22, conduit 23 to accumulator 24. Condenser 22represents a single or series of condensation units at the same orsuccessively lower pressures and temperatures. Preferably, operatingpressure is employed on the condensation unit 22 and accumulator 24. Thetemperature of the efliuent after passage through condensing unit 22 isabout 100 F. In accumulator 24, the desulfurized naphtha is collectedand passed through conduit 26 to separating unit 21 whichrepes'entsconventional equipment for the fractionationY and separation of anaphtha suitable for use in the subsequent hydroforming step. Thisnaphtha stream is free of C3 hydrocarbons andlighter, preferably free ofCe hydrocarbons andv lighter.

Ordinarily, separating unitA 2111s .of conventional designysuitable forremoval of the dissolvedhy- Grav., API 54.2

A. S. T. M. distillation:

I. B. P., oF l143 5% 197 10% 214 20% 238 30% 255 40% 269 50% 280 60% 29370% 306 324 350 370 E. P 415 Recov., per cent 98.0 Residue 1.0 Loss 1.0Aniline point, DF 120 Octane number, CFRM A55 Reid vapor pressure, p. s.i. 1.5 Sulfur, wt. per cent 0.04 Nitrogen, wt. per cent 0.07

turned to the upper portion of extraction unit 33l through inlet conduit34. The gaseous effluent from extraction unit 33 comprises hydrogen andmethane, ethane and propane. This gaseous stream is recyled throughconduit 31 to conduit 4 inorder to supply the excess hydrogen to-thehydrodesulfurization reaction. In the example described in Figure 1, thequantities of net materials, excluding recycle fromhydrodesulfurizationunit 9 are approximately as follows:

Hydrogen sulfide, 31.8 tons per day Ammonia, 2.2 tons per day Y C1 to C3gas (conduit 28), 600,000 standard cubic feet per day e Desulfurizednaphtha (conduit 29), 10,220 barrels per stream day If desired, aportion of the gas in conduit 31 may be Vby-passed to conduit 3| leadingto hydroforming unit 4I, as shown. In vmost instances, howf ever, all ofthe vgas through conduit 31 is returned to conduit 4.

' VThe desulfurizedznaphtha is 4now hydroformed to improve the octanevalue thereof lby increasing its aromatic content. This is accomplishedby passing liquid desulfurized naphtha through Yconduit 29to conduit 3|and thence to a heating and vaporizing zone 38- Recycle gas from thehydrofomiing unit 4| containing hydrogen and relatively low boilinghydrocarbons is introduced into this stream prior to vaporizer 38through conduits 53 and `54, as shown. In vaporizer 38, the naphtha isvaporized and preheated to about the hydroforming temperature employedin hydroforming reactor 4|. If desired, the recycle gases in conduit 53may be introduced into the naphtha feed line after vaporizer 38 by meansnot shown. In such a case an additional preheater, not shown, must beincluded on recycle line 53.

The quantity of recycle gas is approximately 51,000,000 standard cubicfeet per day. The mixture of vaporized naphtha and recycle gas passes ata relatively high velocity through conduit or transfer line 39 tohydroforming reactor 4| of enlarged cross section similar in design toreactor 9. Catalyst is picked up in conduit 39 from conduit or standpipei9. In reactor 4| the gas velocity is between about 5 and about 50 feetper second in order to entrain the catalyst particles in a/relativelydispersed condition in the gaseous reactants. The physical condition ofthe catalyst and gases in hydroforming reactor 4| is substantially thesame as that described with respect to hydrodesulfurization reactor 9.

At the temperature of reaction of about 925 F. ...i

and a pressure of about 480 pounds per square inch gage forhydroforrning react-or 4i, the principal reaction is the dehydrogenationof naphthenic 'hydrocarbons to aromatics. To a somewhat lesser extentaliphatic hydrocarbons are dehydrogenated 'and cyclicized to aromaticcornpounds. 'Some vcracking also occurs, but the hydrogen pressure issuiciently high to saturate substantially all of the cracked productsand to substantially suppress polymerization reactions leading tocompounds higherV boiling than the feed. The combined eiect of thesereactions is endothermic. The external heat required to maintainsubstantially isothermal conditions of approximately 925 F. is16,200,000 B. t. u."s per A hour.

The gaseous eiiluent containing entrained nnely-divided contact materialis withdrawn from hydroforming reactor 4| lthrough conduit 42 andintroduced tangentially into separator 43. In separator 43, the contactmaterial is separated from the gaseous effluent land is passed into astripping zone 44. In stripping zone 44, tarry and carbonaceous depositsand occluded gases are removed from the Contact material. Stripping gasvis introduced into stripper 44 through conduit 46 Aand comprisessimilar gases 'as described With respect to stripper l5 hereinbeforedescribed. The construction and operation of separator 43 and stripper44 are substantially the same as described with respect to separator I2and stripper 5. Stripped catalyst is removed from stripper 44 throughconduit 4T and is passed to transfer line 8 from where it is returned tohydrodesulfurization reactor 9 and the cycle repeated. However, aportion or all of the catalyst may be passed through conduit orstandpipe 48 4for recycle to hydroforming unit 4| in order to controlthe concentration of catalyst therein independent of catalystcirculation throughout Cil the entire two stages of the unit. Generally,the quantity of catalyst recycled to the quantity of catalyst passed totransfer line 8 is about 10:1.

A gaseous effluent comprising treated naphtha, hydrogen and relativelylow boiling hydrocarbons is removed from separator 43 through conduit 4Sand is passed through a condenser 50, a conduit 5| to an accumulator 52.Anycatalyst dust in the eiuent may be removed prior to condensation byconventional means, as previously discussed. Condenser 50 may comprise asingle or series of condensation units similar to unit 22 which reducethe temperature of the eiuent to about 100 F. and condense the naphtha.Treated naphtha is withdrawn as a product of the process fromaccumulator 52 through conduit 56 and is generally stabilized and rerunbefore blending into finished gasoline. The quality and characteristicsof the stabilized and rerun naphtha product are shown in Table IV below:

Grav., API 52.0 A. S. T. M. distillation:

I. B. P., F 103 5% 163 10% 186 212 Y 228 240 251 263 276 295 327 352 E.P 400 Recov., per cent 97.5 Residue 1.0 Loss 39 Octane Number, CFRM 86.9Reid vapor pressure, p. s. i 6.5

Sulunwt. per cent 0.015 Nitrogen, wt. per cent 0.06

Uncondensed vapors comprising hydrogen and relatively low boilinghydrocarbons are removed from accumulator 52 and a portion subjected toconventional recovery processes to recover gasoline boiling rangeconstituents, and another portion is passed through conduit 53 asrecycle to the process. This gaseous material is recycled throughconduit 53 to conduit 8| and, in some instances, a portion may be passedthrough conduit 57 to conduit 4 and thence to hydrodesulfurizationreactor 9.

The quantity of materials obtained as net product of the process fromhydroformer 4i, excluding recycle, is approximately as follows:

Make gas (C1-C3 and H2), 9,100,000 standard cubic feet per day i00% C4gasoline, 8,350 barrels per stream -day 400 F. polymer, 200 barrels perstream day The make :gas is rich lin hydrogen and it may, therefore, besubjected to fractional separation so as to supply a part of thehydrogen consumed in the Vl'iydrodesulfurization step.

Ordinarily, some regeneration of the catalyst is necessary. It ispreferred, therefore, to remove the catalyst for this purpose fromconduit or standpipe i9 through conduit 58, or alternatively oradditionally vfrom conduit 41 by means not shown, and pass it to aconventional regeneration zone 59. In regeneration zone 59, thefinelydivided contact material is contacted with oxygen or air at anlelevated temperature between about 9 '700 and about 1200 F. to burn offcarbonaceous deposits thereon.V The hot regenerated catalyst may be usedto supply a portion of the heat for the hydro forming reaction. Thecatalyst may also be reduced, if desired, without 4departing from thescope of this invention. Fresh catalyst may be introduced into thesystem 'at the same point as the regenerated catalyst.

Although the make-up hydrogen for the process, as described, isintroduced into conduit 4 through conduit I6, this make-up hydrogen maybe introduced conveniently as the stripping gas to stripper l5 throughconduit I8. In such a case, the stripping gas is passed by means notshown from stripper l5 into separator l2 where it is admixed with theeffluent from hydrodesulfurization zone 9. The make-up hydrogen is then'ultimately recycled through conduit 31to .feed line 4. The stripping gasmay be heated to aid in stripping and in maintaining conditionsconducive to the removal of deposits by reactions such as hydrogenationor oxidation.

Specific reaction conditions have been stated for the example describedin connection with the process of Figure 1. A'I'hese particularoperating conditions should not be construed as unnecessarily limitingto the present invention. Both the hydrodesulfurization reaction and thehydroforming reaction may be carried out over a Wide range of operatingconditions. perature employed for hydrodesulfurization may be anytemperature between about 500 and about 1000" F., preferablybetweencabout 700 andabout 925 F. The temperature of` reaction ofhydroforming may be between about 850 and about 1050 F., preferablybetween about 875 and about 950 F. and, in general, higher than 'thetemperature employed for the hydrodesulfurization step. The ,pressureemployed for the hydrodesulfurization step is between about 200 andabout 4000 pounds per square inch gage, preferably between about 300 andabout 1200 pounds per square inch` gage. The pressure for thehydroforming step is between' about 100 and about 1000 pounds per squareinch gage, preferably between about 200 and about 750 pounds per squareinch gage. Since the catalyst is circulated between thehydrodesulfurization zone and the hydroforming zone, it is preferred tooperate both of these reaction Zones at substantially the same pressure.Thus, in the type of operation described with respect to Figure 1 inwhich catalyst is circulated between the reaction Zones, itis preferredto use substantially the same pressure in each of the reaction Zoneswithin the range of about 300 to about 750 pounds different pressures inthe reaction steps is feasible and,under such circumstances, relativelyThe temhigher pressures are employed in the hydrodesulfurization stepthan in the hydroforming step, but within the range previously stated.Itis preferred to use relatively high pressures, particularly in thehydrodesulfurizationy step, in `o rder to minimize the formation ofcoke.

In the hydrodesulfurization step, the mol ratio of hydrogen to chargingstock is generally between about 1:1 and about 30:1, preferably betweenabout 2:1 and about 9:1. In the .hydroforming step, the mol ratio ofhydrogen to naphtha feed charged from the hydrodesulfurization step isless than that employed in the hydrodesulfurization and is generallybetween about 1:1 and about 8:1.

I smaller than 40 microns.

The space Velocity in weight of liquid charged per hour per weight ofcatalyst in the hydrode-` sulfurization reaction zone is between about0.3:'1 and about 15:1, preferably between about 1:1 and about 5:1. Thespace velocity in similar terms for hydroforming is between about 0.2:1and 'about 5:1, preferably between about 0.3:1 and about 2:1.

Variations in the operating conditions between the reaction zones may beachieved in conventional manner. Desired temperatures may be obtained bythe method to be discussed hereinafter.Y Variations in mol ratio ofhydrogen to naphtha charge can be achieved by appropriate recycle ratiosand the particular quantity and location of the introduction of make-uphydrogen. Space velocity is controlled by the rate of feed charged orthe rate of circulation of catalyst to the respective reaction zones.

The gas recycle rate to each of the reaction zones is between about 2000and about 15,000 standard cubic feet per barrel of naphtha charged,preferably between about 4000 and about 10,000 standard cubic feet perbarrel of naphtha charged.

' In general, the catalysts used in the process of Figure 1 comprise theoxides of the metals of the left-hand column of group VI of the periodictable; particularly chromium, molybdenum, and

tungsten are preferred, but other metallic oxides and other metalliccompounds, particularly the oxidesof the metals of the left-hand columnof groups IV and V of the periodic table, such as titanium, seriurn,thorium and vanadium may be used. The sulides as well as the oxides ofthe various metals may be employed, if desired. The metals and theirsulfides of group VIII of the periodic table may also be used, such asplatinum, palladium, nickel and cobalt. While these catalytic oxides andsuliides can be used alone, it is preferable to use them on asuitablesupporting material, such as magnesia or alumina, particularly anactivated alumina or van alumina gel support.V In general, catalyticoxides or other catalytic compounds are present aslthe minorconstituents of the overall catalyst: mass, usually from 1 to40 percentby weight of the total catalyst mass, including the support. It is alsowithin the scope of this invention touse a mixture of catalysts.Preferred catalysts comprise cobalt molybdate, molybdenum oxide,tungsteln sulfide, tungsten nickel sulfide, tungsten molybdenum sulfide,unsupported or supported on activated alumina or alumina gel. When thecatalyst is not circulated between the hydrodesulfurizationzone and thehydroforming zone, two different catalysts may be employed in each ofthese Zones. For example, cobalt molybdate may be employed as a catalystfor the hydrodesul-furization chromium oxide may be employed -as thehydroforrning catalyst.

Preferably, the finely-divided catalyst of this invention contains nomore than a minor proportion by weight of material whose particle sizeis greater than about 250 microns. vThe greater proportion of thecatalyst vmass preferably comprises a material whose particle diameteris smaller than microns, including at least 25 per cent of a materialhaving a particle size An example of a desirable powdered catalyst isone which comprises at least 75 per cent by weight of a material smallerthan microns and at least 25 per reaction and molybdenum` or Y l l centby weight of a material smaller than 40 microns.

Although Figure i has been described with reference to an upwardlyflowing gaseous stream of reactants and catalyst through the respectivereaction zones, it should be understood that the catalyst and reactantsmay ow together downwardly, horizontally, circularly or even angularlythrough a reaction zone at a relatively high Velocity without departingfrom the scope of this invention. However, it has been found that byupward flowing of the gases through a substantially vertical reactionzone the entrainment of the catalyst and the residence time thereofinaybe controlled conveniently. and accurately and the tendency forsegregation and stratification of the catalyst is minimized.

Extraneous feed stocks, such as naphthas or kerosene, may be introducedinto the system between stages, such as into conduit 3| by means notshown. Steam may also be used to replace at least a\portion of the addedhydrogen in the process. Thus, for example, steam may be introduced intoconduit i through conduit 5 and the steam reacts with thel sulfur inhydrodesulfurizer 9 to produce hydrogen sulde.

According to this invention the exothermic heat liberated by thehydrodesulfurization reaction is transferred to the endothermichydroforming reaction by indirect heat exchange between the reactionzones with the use of a coolant vapor compressor. The reactions aremaintained under substantially isothermal conditions in the followingmanner: A suitable vaporizable liquid medium, such as mercury, is passedfrom reservoir 6I through conduit 62 to heat exchanger 63. The liquid,which in the example of Figure l is mercury, is vaporized in heatexchanger 63 which is suitably disposed in hydrodesulfurizer 9 in heatexchange with the reactants. The pressure of the mercury is held atabout 40 pounds per square inch gage, of which pressure the vaporizationtemperature is about 825 F. in heat exchanger G3. drodesulurizationreaction of the example of Figure 1 liberates about 16,700,000 B. t. u.sper hour which in turn evaporates about 141,000 pounds of mercury perhour. The evaporation of the mercury absorbs the exothermic heat ofreaction of reactor 9 by latent heat of vaporisation.

The mercury vapor thus evaporated is removed from heat exchanger 63through conduit 64 and returned to reservoir 6l. Reservoir 6I ismaintained at the operating pressure of about 40 pounds per square inch`gage. Mercury vapors are removed from reservoir 6l through conduit l andpassed through conduit'll to a two-stage turbo-compressor 'i2 in whichthe vapor is compressed to a pressure of 120 pounds per square inch gageand the temperature is raised to about 1175* F. Two stag of compressionwith interstage-cooling are used because the low specific heat of themercury vapor results in a tendency towards excessive temperature riseduring compression. The compressed mercury at a temperature of about1175 F. and about 120 pounds per square inch gage is passed fromcompressor 12 through conduit 'i0 to heat exchanger 16. Mercury vaporflows through heat exchanger 16 in indirect exchange with the reactantgases in hydroforrner di and supplies the 16,200,000 B. t. u.s per hourof heat required for hydroformer 4l. The removal of heat from themercury vapor at As previously discussed, the hythe pounds pressureresults in its condensation at approximately 950 F. in heat exchanger76. Liquid mercury is removed from heat exchanger 15 through conduit Tiand is expanded through expansion valve 18 into conduit Sii. Duringexpansion of the mercury in valve 18, a small portion of the mercury isagain vaporized. The mercury in conduit 655 is recycled to reservoir Sl.

Since the hydrcforming heat duty is slightly less than that removed fromthe hydrodesulfurization reactor and also because of the heat added tothe compressed vapor as work, the quantity of vapor required to becondensed in exchanger "i6 is less than that vaporized in heat exchanger63, this amount being about 133,000

pounds per hour. The remainder or about 8,000 pounds per hour of mercuryVapor plus the amount resulting from the dashing of the 120 pounds persquare. inch gage mercury condensate through valve 'i8 are passed fromreservoir El through conduit 6l to condenser 68 to remove excess heatand the resulting condensate returned to reservoir G l, as shown, inorder to balance the system.

The operation of compressor l2, which has an overall eiciency of about70 per cent, consumes about 800 horsepower. Since the heat equivalent ofone horsepower hour is about 2,545 B. t. u.s, 16,200,000 B. t. u.s perhour are recovered and made available at the higher temperature levelrequired for hydrofcrmer QI at an energy cost corresponding to onlyabout 2,040,000 B. t. u.s per hour.

As shown in elevation, the condensate from condenser 58 is passed toreservoir 6l by the static head of the condensate in the conduitconnecting condenser E3 and reservoir 6l. Should this static head beinsufficient to pass the condensate from condenser 68 to reservoir 0i,the required amount of vapors to balance the system may be removed fromthe downstream side of compressor l2 through conduit 13 and passed tocondenser 68 at an elevated pressure.

While mercury is used as a thermodynamic huid or heat transfer medium inthe example of Figure 1, any stable high-boiling liquid may be usedwithout departing from the scope of this invention. Preferably, theboiling point of the heat transfer medium should be about 800 F. orlower in order to avoid sub-atmospheric pressures on the heat inputside. Another suitable highboiling heat exchange iiuid for use in thepresent system is a close-cut fraction or the hydroformer polymer itselfproduced bythe chemical process shown in Figure l. This high-boilingpolymer is highly aromatic and, therefore, heat stable. Although heatexchange with reactor 0 is shown as downflow and with reactor lll asupiow, heat exchange with the reactors may be both upflow or bothdowniiow without departing from the scope of this invention.

The indirect transfer of heat from the low temperature exothermicreaction to the high temperature endothermic reaction in the mannerdescribed is highly advantageous since it minimizes the amount ofpreheating necessary for the hydroformer feed stock. As would beobvious, the use of high preheat temperatures characteristic of theprior art results in undesirable thermal decomposition and also makes itimpossible to obtain isothermal conditions in the reaction zone.

The high velocity system shown for both hydrodesulfurization andhydroforming has certain particular advantages which make such a systempreferable to conventional nuidized dense phase catalyst operationsHydrodesulfurization and hydroforming are not like many reactions, suchasthe hydrogenation ofcarbon monoxide to produce organic compounds,which reactions may be effected at low conversions per pass withrecycling of the reactants to increasethe overall conversion. In thetype of reactions discussed in this application, high conversions mustbe achieved, if at all, in a single passwithout recycling. In luidizeddense phase operations due to the low gas velocities, high conversionsper pass are dicult. 'I'his difliculty arises from the internalcirculation of reactants and catalyst in the reactor resulting in .ampleresidence time for some material but insufficient residence time forother material. The high velocity system for concurrent flow of catalystVand reactants obviates the above difficulties. In the high velocitysystem both the residence time of the catalyst andreactants are undercontrol inasmuch as there is a minimum of internal circulation.Subquently subjected to hydroforming and the heat the same manner asdescribed with respect to stantially complete removal of sulfur can beobtained in a single pass by the high velocity technique. Numerous otheradvantages are apparent wit the high velocity A system which cannot beobtainedreadily with a conventional iluidized dense phase operation. Inthevhigh velocity system the residence time of the catalyst in thereaction zone is relatively short as compared to the dense phase type ofoperation and between each pass of the catalyst through the cycle of thehigh velocity system the catalyst is stripped of tarry and carbonaceousdeposits and occluded gases. This frequent stripping of the materialsmaintains the catalyst at its maximum activity and increases Y the lifeof the catalyst; in some cases eliminating entirely regeneration of thecatalyst. The high dispersion and rapid movement of the catalyst in thehigh velocity type ofoperation also minimize the sticking together ofthe catalyst particles as a result of the accumulation of tarry andcarbonaceous deposits thereon. The dispersed condition also accounts fora more smooth reaction and minimizes the chance for overheatingfrequently accompanying exothermic reactions. The high velocity systemalso is characterized by full control of the concentration of thecatalyst in the reaction zone, this concentration being a directfunction of the velocity of the reactants :and theloading rate of thecatalyst into the gas stream. This is not true of the dense Aphaseoperation where the concentration is essentially a function of thevelocity only. Still a further advantage of the high velocity system is-that at the higher velocities characteristic of this system heattransfer between the walls of the heat exchange means andthe reactantsis very efficient as the gas. lm resistance'is minimized.

With regard to the heat transfer mechanism between the two different'reaction zones, vthis Figure 1 and the heat liberated by the desulfurization reactions is absorbed by a stream of the same heat transfer mediumand passed to a reservoir where the vapors are compressed and Athenpassed to the heat exchanger of the hydroforming reaction zone.

Although the invention has been described with respect tohydrodesulfurizationof a suitable hydrocarbon fraction, selectiveoxidation of the sul- -fur with oxygen or air may be carried outin'substantially the same manner as described with respect to thehydrodesulfurization reaction. The

,primary differences are the substitution of oxygen for hydrogen in thehydrodesulfurization reactor and the removal of sulfur dioxide from theeiiiuent of the desulfurization reactor lby distillation rather than byextraction' or absorption. The same catalyst may be employed foroxidation of the sulfur as with the hydrodesulfurization reactionVdescribed hereinbefore. However, in oxidizing the sulfur it ispreferred to use'vanadium pentoxidedeposited on silica gel for thesulfur removal stage. f

In the previous discussion of the invention the contact material wasreferred to as 'a catalytic material, but it is within the scope .ofthis inV'en-Y.

terial is generally between about 1:10 to about 1:1 by'weight. e

The upgrading or improvement in quality 'of petroleum distillates by thecombination of hydrodesulfuriz-ationV and hydroforming in separatesteps, as shown by Figure 1, has numerous advantages; Most largerefineries, even those ade'- `quately equipped with catalytic capacity,produce method of heat transfer may be applied to stational-y bedreactors and fluidized dense phase drodesulfurized. While thehydrodesulfuriza'tion of a naphtha fraction has particular utility inthe presentl invention, since this fraction is subse- 'a substantial'amount of thermally cracked Vgasoline, generally as much as 25 per centor more of the totalgasoline output.' Ihe'source'sv of these stocks'aregenerally visbreaking or coking,'cycle stock cracking and straight runnaphtha reforming operations. By todays standards the quality of suchfractions is comparatively'low, averaging perhaps 70 C. F. R. M. octane,with poor `stabilityjarid tetraethyl lead response. 'In addition, thesethermally cracked fractions are frequently high in sulfur compoundswhich are not yremovable by conventinoal methods, In the past olinesfromcatalytic cracking or hydroformin'g.

However, in ViewV of presentday standards of in'- creased quality andthe amount of increase'in sour crudes, the utilization of such:thermal-ly cracked fracti'onsis` becoming a critical problem to. manyrefiners.

Hydroforming alone. is not: a satisfactory solution to the vaboveproblem. because of t1 e low yield of product of suitable octane number,high coke yields, the requirement for corrosion resisting materials ofconstrution, and the pollution of the surrounding atmosphere With sulfurcompounds. The combination process of hydrodesuliurization andhydroforming has, therefore, become of great importance and the need forimproving thev efficiency and operability or such processes is apparent.process as described with respect to Figure l overcomes essentially allor the above difficulties and is. commercially feasible, particularlywhen the use of a high velocity concurrent system is employed.

As previously stated, Figure 2 of the drawing isa diagrammaticillustration ofmulti-stage heat exchange which may be convenientlyemployed on hydrodesuliurization reactor 9 and hydroforming reactor 4|of Figure l. The use of the multistage heat exchange on the reactors, asshown,

enables more close temperature control of the varied, which temperaturecontrol by a single heat exchanger is dinicult. Further, it may be Thecombination desirable to maintain different temperature levels atdifferent points in the reactors which can be achieved best by the useof multi-stage heat exchange.v Figure 2 is a suitable set-up formaintaining different temperature levels T1, T2, T3 and T4 in reactors 9and 4I of Figure 1. It is to be understood, however, that the sameset-up may be used when the quantity of heat to be removed is differentat different points in the reactors, even when T1 and T2, and T3 and T4are to be maintained at substantially the same levels, respectively.According to Figure 2, temperature T1 is maintained substantiallyconstant by maintaining a pressure P1 in reservoir |0| such that theheat exchange fluid boils at a temperature suitably related to T1. Theliquid heat exchange medium, such as mercury, is passed from reservoir|0| under pressure P1 through conduit |02 to heat exchanger |03 Wherethe liquid boils at a temperature corresponding to pressure Pi. Thevapors of the heat exchange medium are removed from heat exchanger |03through conduit |04 and returned to reservoir |0|. Vapors are removedrom reservoir |0| through conduit |08 to be passed to the heat exchangeunit or hydroforming reactor 4| as to be discussed further hereinafter.In another portion of reactor 9. temperature T2 is maintained byadjusting the pressure P2 of reservoir |01 at the required value. Liquidheat exchange medium is Withdrawn from reservoir |01 through conduit |08and passed to heat exchanger |09. In heat exchanger |09, the liquid heatexchange medium Vis vaporized at a temperature corresponding to pressurePz. Vaporous heat exchange medium is withdrawn from heat exchanger |03throughV conduit E and passed to reservoir |01. Vaporous heat exchangemedium is Withdrawn from reservoir |01 through conduit I2 to be passedto the heat exchange unit offhydroforming reactor 4| as to be discussedhereinafter.

The exothermic heat of hydrodesulfurization unit Sismade available tohydroforming unit 4| 'Ihev arrangement of apparatus in :V

by passing the vaporizedheat exchange medium from conduit |06 tocompressor E. In compressor IIB, the vapors are compressed in a similarmanner as described with respect to Figure 1 to pressure P3 whichcorresponds to the pressure necessary to maintain a temperature of theheat exchange medium suitably related to temperature T3 at thatparticular point shown in reactor 4|. The compressed vapors are passedfrom compressor I|6 through conduit ||1 to heat exchanger IIS. In heatexchanger H3 the compressed vapors are condensed at a temperaturecorresponding to pressure P3, giving up their latent heat ofcondensation to the reaction mixture in the upper portion of reactor 4|.Condensed heat exchange medium is passed from heat exchanger I8 throughconduit I9 to conduit |2| and then returned to reservoir lili afterexpansion through an expansion valve in line H9. Similarly, vaporousheat'exchange-medium from reservoir |01 is passed through conduit H2 tocompressor |23. The vaporous heat exchange medium is compressed to apressure P4 in compressor |23. The compressed vapors are passed fromcompressor |23 through conduit |24 to heat exchanger |26. In heatexchanger |26, the compressed vapors are condensed at a temperaturecorresponding to pressure P4 and give up their latent heat ofcondensation to the reactants in the lower portion of hydroformer 4|.Condensate is passed from heat exchanger |26 through conduit |21 and anexpansion valve to reservoir |01.

If the exothermic heat of the hydrodesulfurization reaction effected inreactor 9 is greater than that necessary to supply heat to theendothermic reaction effected in reactor 4| and to maintain thetemperature at the desired level or levels therein, a portion of thevapors in conduits |00 and/or I2 is removed therefrom through conduit|3| and passed through conduit |32 to condenser |33. This portion of thevapors is condensed in condenser |33. From condenser and cooler |33condensate is returned to the system through conduits |34 and |36. Thiscondensate may be passed directly to reservoir |'0I or directly toreservoir |01 or may be split and passed in the appropriate proportionsto both reservoirs |0| and |01 as shown. In some instances the amount ofheat available from hydrodesulfurization reactor 9 or from anyexothermic reaction which may be effected therein and the compression ofthe heat exchange vapor may be insuincient to supplyV the requiredamount of heat to the reaction eected in reactor it In such case theadditional heat required is obtained by passing condensate from conduitsH9 and/or |21 through conduit |38 and conduit |39 to vaporizer MI. Invaporizer |4|,'the required amount ofl make-up heat is added to thesystem by the vaporization of that portion of the condensate removedthrough conduit |38. The vapors produced in heater are passed throughconduit |36 and returned to the system through conduit 2| and/or conduit|21. These vapors may be passed directly to reservoir lill, or reservoir|01, or may be split and passed in appropriate proportions to reservoirsi 0| and |01, respectively.

The above arrangement of apparatus is an effective manner formaintaining different temperature levels in the exothermic andendothermic reactors as Well as maintaining a constant temperaturethroughout the reactors Where the heat liberated or absorbed isdifferent for diierent locations Within the reactors. Nu-

finerous combinations are available in thev arrangement shown in Figure2. Temperature T1 may be higher than temperature vTz `and temperature T3may 'be higherV than temperature Ti in one combination. In anothercombination, T1 and T2 may be .at the same temperature `level and T3 andT4 may be at thesame but higher tempera.- ture level, but the heatk.duty at T2, 'Ib and T4 may be different as the result of differentrates of reaction at each locality. In still another combination, T2 maybe greater than T1 and T4 may be greater than Ta'. It is also within thescope of this invention yto have the `temperature of T1 less than thetemperatur eoi T2 but at the same time 'having temperature Tagreaterthantemperature T4. In each of the above combina'- tions pressures P1,VV Pz,Pa and P4 mustv be adjusted accordingly. f

The arrangement ofv apparatus and heat exchangers of Figure 2 areparticularly adaptable lwhere a second exothermic reaction (not-shown)is being eiected in the overall process', from which additional heat maybe available for heating up the reaction in the endothermic reactor suchas in reactor 8|. For example', a heat exchanger may be inserted in thecatalyst regeneration zone, such as regenerator 59'of Figure 1, andconnected to the heat exchange system in a marmer similar to heatexchanger |63 or |09. The regeneration of the catalyst -is largelyachieved by oxidation of carbonaceous deposits, which reaction is exoathermic. The arrangementv shown in Figure 2 may also be employed when'`a gas oil or reduced crude is being hydrodesulfurized in a separatereactor fromwhich heat may bel made available by the system disclosed inFigure 2.

The multi-stage heat exchange system of Fig ure 2 is particularlyadaptable Where multi-stage hydrodesu'lfurization is effective as theyheat liberated in each stage ofthe hydrodesulfurization may be differentand-therefore, to take advantage of this liberated heat it is necessaryto employ separate heat exchangers foreach Zone and pass the heat thusrecovered tothe endo.- -thermic zone, such as endothermic zone 4| .ofFigure l. Figure 3 is a diagrammatic illustration .of an arrangement ofapparatus- -for effecting multi-stage hydrodesulf-urization. Multi-stagehydrodesulfurization isV particularly advanta geous, as previouslypointed out. since influidized processes it .is substantially impossibleto obtain maximum .or high degree of decid-urination unless someprovsonis made :for minimizing internal circulation of catalystsfreactants. Fluidized hydrodesuliurization can best be .effected by theconcurrent vhigh velocity process, and maximum ei'iciency ,even ofthis'process is achieved by eiecting the .desulfurization reaction instages. According to this modcaton of the invention, a suitable naphthafeed stock `clrltaiiling sulfur is passed through conduit |5| to heater`and vaporizer |53. Makefup hydrogen is introduced-into conduit |5|through conduit |52. Vaporized naphtha is passed-through conduit |54 toa rst stage hydrodesulfurization reactor |56. Contact material isintroduced into the stream of vaporized naphtha and hydrogen in conduit|54 through conduit |18. The reactants and .oo ntact material passupwardly l.through reactor 1.56 in contact withheat exchanger 51. Y'iheeiliuent from the rst stage hydrodesu liurizationV containing entrainedcatalyst ,ispassed throughccnduit |59 to catalyst separator 16|. incatalyst Separator il Catalyst. is' separated trom navetta hydrogensulfide and hydrogen and settles-.into

stripper |62. ySeparator |.6I and stripper |62 are substantially thesame as the corresponding sepa.,- rator and stripper described in Figure1 of the drawings. A .suitable stripping gas, such as hy.- vdrogen orsteam, isintroduced into stripperV |62 through conduit |63. Strippedcatalyst is re.- moved from stripper |62 through a conduit .orkstandpipe |64.

The partially desulfurized naphtha and hydro.- gen are removed fromseparator |6| ythrough conduit l' and passed .to the second stage.hydrof desulfurization unit |69, in.which desulfurization of the feedstock is completed. Stripped catalyst from the rst stage reaction isintroduced into conduit |68.through conduit |66,` as shown. A portion ofthis stripped catalyst may be recycled -to the rst stage desulfurizationunit 56 lthrough conduit |81, if desired. Vaporized naphtha'hy.- .drogen.and entrained catalyst are'passed up.- -wardly through second stagereactor |69 in contactwith heat exchanger |1|. The effluent. from thesecond. stage rhydrodesulfurir/:ation unit |69 is withdrawn throughconduit |12 and passed to .catalyst separator |13 in which entrainedcatalyst is separate'dfrom the reaction eiiiuent. The en.- `trainedcatalyst settles into stripper |14. A suit.- able stripping gas such ashydrogen or steam i-s introduced into stripper |14 through conduit |16.Separator |13 .and stripper |14 are substantially thev same as separator.|6I and stripper |62.

Stripped catalyst is withdrawn from stripper ,|14

and passed to inlettconduit` |54 through conduits vor standpipes |11 and|18. AA portion of the stripped catalyst from ther second stagedesuliurization unit may be recycled to conduit .|68 through conduit'|19, if desired.

The naphtha eiiluent' substantially free from .organically .combinedsulfur is removed from separator |13 through conduit |8| and passedthrough conduit' |82 to a conventional condensa.- tion lstage |83. Thecondensation stage |83 may comprise a series of .condensation units atthe samepressure or at successively lower pressures. Condensate ispassed from condenser |83 to accumulator |84. From accumulator |84, thede.- sulfurized naphtha is withdrawn through conduit |86 as a productofthe process. The fraction recovered from conduit |86 may be subjectedto further treatment, such as hydroforming. Un.- condensed vapors'comprising hydrogen, hydrogen sulde, methane, .ethane' and otherrelatively lowv boiling hydrocarbons are removed'vfrom accumu- -lator|84 through .conduit |81 and a portion of this .vaporousst'ream may ibevented tothe atmosphere to prevent the build-up of ethane and methane inthe'rprocess. Av major proportion of the-vapor stream is recycled afterremoval of hydrogen .sulde' as in Figure :1, ythrough conduit |88 tofeed line |54 to .supply the added hydrogen to the process. A .portionof the Y'vapor .stream containing hydrogen'ma'y be'p'assed throughconduit |88 to conduit |68 in order to control the hydrogen content ofreactor |69 independent or" reactor |56, if desired.k

It is preferred to introduce fresh catalyst into the systemthrough'conduits l|92`or I-Sbetween the rst and second stage oftheprocess. Apc-rtion'of the `effluent withdrawn from the rst stage of theprocess may be Icy-passed and passed-to condenser |83 through :conduit|9|, if desired.

In the arrangement of apparatus shown, heat exchanger ,|51 may.convenient-ly constitute heat eXChanggr |09 0f Figure 2 and heatexchanger |11 may censtitute heat exchanger .m3-.lof Figure a Heatexchanger |51 and |1| may also be con- `Figure l.

'nected in series as a singleA exchanger and connected in the systemlike shown in Figure l.

In general, the reaction conditions and method of operation are similarto those described with respect to the hydrodesulfurization unit 9 ofFigure 1. It is possible and often desirable to maintain the first andsecond stage desulfurization at different conditions when using amulti-stage hydrodesulfurization process. Thus, it is desirable tomaintain the second stage hydrodesulfurization reaction at a temperatureat least 50 F. higher than the rst stage and preferably above 800 F.,but within the range disclosed With respect to reactor 9 of Figure l.

.At such higher temperature in reactor 69, de-

sorption, Vaporization andl destructive hydrogenation of carbonaceousdeposits and tars deposited upon the catalyst is eiected and a ina--terial increase in the length of the catalyst life is observed. Underoptimum operating conditions regeneration of the catalyst may beeliminated entirely. VIt may also be, desirable to maintain the hydrogen-content in the secondl .stage hydrodesulfurization higher than the rststage. In' the preferred modification of Figure 3, the hydrogen contentin terms of mol ratio of the first stage is Amaintained approximately.half that Yof the second stage but within the range as disclosed withrespect to reactor 9 of It may be also desirableto maintain the reactionpressure of the second stage hydrodesulfurization at a higher pressurethan in the first stage. In such a modification, the hydrogen content ofthe reaction mixture may be substantially the same in both stages, butthe partial pressure of the hydrogen may be substantially greater in thesecond stage. Increase in pressure has a similar effect as an increasein temperature and aids in the destructive hydrogenation of carbonaceousand tarry deposits from the catalyst. Under the preferred operationconditions for the two-stage process of Figure y3 between about 50 andabout '10 per cent of the organic sulfur is converted in the rst `stageand the remainder ,of the sulfurY up to about 90 to 100 per cent isconverted inthe second stage. Although only two stages of operation areshown for the modication of the invention of Figure 3, three and fourstages or more may be employed without departing from the scope of thismodification.

A similar `operating technique of multi-stage operation may be employedto eiect hydroforming. In hydroforming .by multistage. process the.operation` is carried out substantially the same as that described withrespect to Figure 3. It isparticularly desirable in the case ofhydroforming to carry out the second or last stage of the process at ahigher temperature than the rst stage in .order to completearomatization.

temperature increase of at least 25 F. is preferred in the case ofhydroforming in a multistage process.

It is within the scope of the present invention to employ a condensationstep between the rst ,and second stage of the multi-stage processdescribed with respect to Figure 3. Condensation between stagesmay bedesirable in order to have independent control over the quantity andquality of recycle gases to the respectively stages.

It may also be desirable to remove the hydrogenv urel.

In another modification of the present inven= tion, thehydrodesulfurization step may employ thehigh velocity techniqueasshownin Figures l-and 3`follov'ved b'ya hydroforming step. conducted insucham'anneras to maintain the catalyst in the so-called.pseudo.liquiddense phase condition. This .particular type of operation may vbedesirable in order to obtain increased contact times in the secondhydroformirlg ree action step, whereas'ithe high velocity type ofOperation maybe .preferable for the hydrodesulffurization type becauseof Ythe relatively short contact times permissiblamg...

'Ihe drawings of the'present invention diagrammatically illustrate`various modications of the invention. Various pieces 'of equipment suchas compressors, storagefvessels, condensers and coolers, fractionationand extraction equipment, etc., have beenreliminated from the drawingsas a matter of convenience and clarity and their use and location willbecome apparent to those skilled in the art.

Although, the invention has been described with particular reierencetodehydrodesulrization and hydroiorming, the invention may be applied toother combination processes employing both exothermic and endothermicreactions in which the exothermic reaction is carried out at a lowertemperature than the endotherinic reaction. For example, the inventionapplies to synthesis gas making and synthesis, hydrogenation andhydroforming, synthesis reaction and catalytic cracking or reforming ofa product thereof, synthetic phenol- (1) chlorination of benzene and (2)hydrolysis of chlorobenzene, and many other chemical processen.

I claim:

1. In an integrated process for effecting chemical reactions involvingthe reaction steps comprising an exotherrnic reaction and an endothermicreaction, such as hydrodesulfurization and hydroforming, selectiveoxidation of sulfur and hydroforming, synthesis gas making andsynthesisl hydrogenation and hydroforming, synthesis and catalyticcracking of synthesis product, synthesis and reforming of synthesisproduct, and chlorination of benzene and hydrolysis of cholorobenzene inwhich reactant is passed successively through the reaction steps and inwhich the exothermic reaction step is eiected at a temperature nothigher than the endothermic reaction step and the heat released by theexothermi-c reaction step is not equivalent to the heat required by theendothermic reaction step, the method for supplying the required heatfor the endothermic reaction which comprises indirectly contacting withthe exothermic reaction a vaporizable heat exchange liquid under apressure such that heat exchange liquid is vaporized at a temperaturesuitably related to the temperature of reaction, compressing vapor thusproduced by indirect heat exchange with said excthermic reaction,indirectly contacting with the -endothermic reaction vapor thuscompressed at a pressure such -that vapor is condensed at a temperaturesuitably related to the temperature of reaction, returning condensateproduced by heat exchange with the endothermic reaction at a lowerpressure for heat exchange with the exothermic reaction, removing aportion oi the heat exchange medium from theabove heat exchange cycle,regulating the heat content of this portion of the heat exchangel mediumremoved from the heat exchange cycle to balancetheheatY requirement ofthe 21 system, and thereafter returning thislatter portion of the heatexchange medium to the heat exchange cycle.

2. In an integrated process for effecting chemical reactions involvingthe reaction steps corn.- prising an exothermic synthesis reaction andanendothermic cracking reaction in which reactant is passed successivelythrough the reaction steps and in which the exothermic reaction 4step iseiected at a temperature not higher than the endotherrnic reaction stepand the heat released by the exothermic reaction step `is greater than.the heat required bythe endothermic step, the

method Yfor supplying the required heat for the endo'thermic reactionwhich comprises indi.- rectly contacting with the exothermic reaction avaporizable heat exchange liquid under a pres.- suresuch that heatexchange liquid is vaporized at a temperature suitably related to thetemperature of reaction, compressing a .major proportieriv of the vaporthus produced. by. indirect heat exchange Vwith said exothermicreaction, indirectly contacting with the endothermic reaction vapor thuscompressed at a pressure such that vapor isv condensed at a temperaturesuitably related to the'temperature .of reaction, returning condensateproduced by heat exchange with the exothermic reaction at a lowerpressure for heat exchange With the exothermic reaction, removing aminor proportion of the heat exchange vapor from the above heat exchangecycle, condensing the vapor thus removed from the heat exchange cycle,and thereafter returning the resulting condensate to the heat exchangecycle. t

3. In an integrated process for effecting chemical reactions involvingthe reaction steps comprising an exothermic synthesis reaction and anendothermic gas making reaction in which reactant is passedvsuccessively through the reaction steps and in which `the excthermicreaction step is effected at a temperature not higher than theendothermic reaction step and the heat released by the exothermicreaction step is less than that heat required bythe endo.- thermicreaction step, the method for supplying therequired heat for theendothermic reaction lwhich comprises indirectlyr contacting with theexothermicreaction a vaporizable heat exchange liquid under a. pressuresuch that heat exchange liquid is vaporized at atemperature suitablyrelated to the temperature of reac- ',moving a minor proportion of thecondensate produced by heat exchange with the endotherinic reaction fromthe alcove heat exchange `cycle, vaporizing the condensate rthus removed`from the heat exchange cycle, and thereafter `rctilllling the resultingvapor to the heat exchange Cycle.

4. In an integrated process for Qiectinschemical reactions involving thereaction steps cornprising an exothermic hydrodesulfurization reactionand an endothermic hydroforming rea-ction in which reactant is passedsuccessively `through the reaction steps and in which the exothermicreaction step is effected at a temperapoffchlorcbenzenen which reactantis passed fsuccessively throughthe reaction steps "and in '75whichftheexothermic'reaction step is effected at turenot higher than thendothermic reaction step and the heat-released by the exothermicreaction step is not 4equivalent to the heat re.-

rquired by the rendothermc reaction' step, the

method for supplying the `required heat for the endothermicreactionwhich comprises a plurality of heat exchange'circuits betweensaid exothermic `and said endothermic reaction steps, each of said heat'exchange circuits comprising indirectly contacting with the exothermicreaction a vaporizableheat exchange liquid under a pressure suchthatheat exchange liquid is vaporized -at a temperature suitably relatedto the desired reaction temperature, compressing vapor thus produced byindirect heat exchange with said exothermic reaction, indirectlycontacting with the endothermic reaction vapor thus compressed at apressure such that vapor iscondensed at a temperature suitably relatedto the .desired reaction temperature. returning condensate produced byheat exchange with the endothermic reactionatxalower pressure for heatexchange with the :exothermic reaction and to complete the .heatexchange circuit, removing a portion ofi the heat .exchange medium fromthe plurality cfr heat exchange Vcircuit-s, regulating the heat contentVniet-his :portion of the heat exchange medium `removed fromztheplurality of heat .exchange circuits Vto balance the heat requirement ofthe ventire system,v .and vthereafter returning thisvlatter portion .ofthe .heat exchange .medium to -thepluralityxof heat exchange circuits.

.i 5. In an4 integrated process for effecting chemical reactionsinvolving the reaction steps com- -prisingan exothermic reaction and an`.endothermic reaction, such as hydrodesulfurization and .hydroiorminglselective oxidation'of sulfur and .hyd-reforming; synthesis gas :making.and synthesishydrogenation and hydroforming, synthesis and.catalyticcracking `of synthesis product, synthesis and reforming `ofsynthesis product, and chlorination of. benzene and hydrolysis offchlorcbenzene in which reactant is passed successively through thereaction steps and in which the exothermicreaction step is effected at atemperature, notfhigher than the .endothermic -reactionsteu the methodfor supplying the -required heat for the endotherrnic reaction whichcomprises indirectly --contacting with the .exo-

therrnic reaction a vaporizable heat exchange contacting with theendothermic reaction vapor thus compressed at a pressure such that vaporisr condensed at a .temperature suitably related to the temperature ofreaction, and returning .condensate produced .by heat exchange with .theendotherrnic reaction at .a lower pressure for heat exchange. with theexothermic reaction.

. o. In an integrated process for effecting chemical `reactions.,involvingthe reaction steps .coinprising an exothermic reaction andanendothermicA reaction,v ,such as hydrodesulfurization and hydroforming;selectiveoxidation .of sulfur and hydroforming,Y-.synthesisr gas makingand synthesis, hydrogenation and hydroforming, syn thesis and catalyticcracking of synthesis product, synthesis-and reforming of synthesisproduct'andchlorination of benzene and hydrolysis a temperature nothigher than the endothermic reaction step, the method forsupplying therequired heat for the endothermic reaction which comprises a pluralityof heat exchange circuits between said exothermic and said endothermicreaction steps, each of said heat exchange circuits comprisingindirectly contacting with the exothermic reaction a vaporizable heatexchange liquid under a pressure such that heat exchange liquid isvaporized at a temperature suitably related to the desired reactiontemperature, compressing vapor thus produced by indirect heat exchangewith said exothermic reaction, indirectly contacting with theendothermic reaction vapor thus compressed at a pressure such that vaporis condensed at a temperature suitably related to the desired reactiontemperature, and returning condensate produced by heat exchange with theendothermic reaction at a lower pressure for heat exchange with theexothermic reaction and to complete the heat exchange circuit.

'7. In an integrated process for eiecting chemical reactions involvingsuccessive steps comprising an exothermic relatively low temperaturehydrogenation reaction and a subsequent endothermic higher temperaturehydroforming reaction, the improvement which comprises vaporizing aliquid by indirect heat exchange with said exothermic reaction,compressing vapor thus produced, condensing Vapor thus compressed byindirectfheat exchange with said endothermic reaction, and returningresulting condensate to 4said exothermic reaction whereby heat istransferred from said relatively low temperature `excthermic reaction tosaid higher temperature endothermic reaction.

8. In an integrated process for effecting chemical reactions involvingsuccessive steps comprising a relatively low temperature exothermicselective oxidation of sulfur reaction and a higer temperatureendothermic hydroforming reaction, the improvement which comprisesvaporizing a liquid by indirect heat exchange with said exothermicreaction, passing vapor thus produced to an accumulation zone, removingaportion of the vapor from said accumulation zone, compressing theaforesaid portion of vapor from said accumulation zone, condensing vaporthus compressed by heat exchange with said endothermic reaction, passingresulting condensate from said endothermic reaction to said accumulationzone,

passing condensate from said accumulation zone in heat exchange withsaid exothermic reaction to vaporize same as aforesaid, removing anotherportion of the vapor from said accumulation zone, separately condensingthis latter portion of the vapor from said accumulation zone, andreturning resulting condensate to said accumulation zone.

9. In an integrated process for the treatment of a hydrocarbon fractioncontaining sulfur to remove sulfur and to improve the motor fuel qualitythereof involving Ythe successive steps comprising hydrodesulfurizationat a relatively low temperature and the subsequent hydroformc ing of thedesulfurized stock at a higher temperature, the improvement whichcomprises Vaporizing liquid by indirect heat exchange with thehydrodesulfurization reaction, compressing Vapor thus produced,condensing vapor thus compressed by indirect heat exchange with thehydroforming reaction and returning condensate from heat exchange withthe hydroforming reaction for heat exchange with thehydrodesulfurization reaction whereby vheat istransferred from saidYrelatively low temperature hydrodesulfurization reaction to said highertemperature hydroforming reaction.

10. In an integrated process for the treatment of a' hydrocarbonfractionv containing sulfur to remove sulfur therefrom and to increasethe aromatic content thereof involving the successive steps comprisinghydrodesulfurization at a relatively low temperature and the subsequenthydroforming of the desulfurized feed stock at a higher temperature, theimprovementrwhich comprises vaporizing a hydrocarbon feed stockcontaining sulfur and passing same upward through an elongatedhydrodesulfurization zone in the presence of a finely-divided catalystat a gas velocity eilective to suspend the nely-divided catalyst-in thegaseous reaction mixture and to move finely-divided catalyst in thedirection of flow of the gaseousreaction mixture through saidhydrodesulfurization zone, removing from said hydrodesulfurization zonean eiiluent containing entrained finely-divided catalyst and hydrogensulde, removing hydrogen sulde and finely-divided catalyst from saideiliuent of said hydrodesulfurization zone, passing the eiiiuent of saidhydrodesulfurization zone substantially free from hydrogen sulfide andin the vapor state upward- 1y through the elongated Ihydroforming zonein the presence of a finely-divided catalyst at a gas Velocity eiectiveto suspend the nely-divided catalyst in said gaseous mixture and to movefinely-divided catalyst in the direction of flow of the gaseous mixturethrough said hydroforming zone, removing from said hydroiorming zone aneiuent of increased aromatic content and containing entrainedfinely-divided catalyst, separating iinely-divided catalyst from theeffluent of said hydroforming zone, recovering the hydroforming eiuentas a product of the process, passing separated catalyst from saidhydrodesulfurization eiliuent to said hydroforming reaction zone andpassing separated catalyst from said hydroforming eluent to saidhydrodesulfurization reaction zone, maintaining the hydrodesuliurizationzone at a temperature between about 700 and about 925 F. and maintainingthe hydroforming zone at a temperature between about 875 and about 950F., maintaining the pressure of both the hydrodesulfurization i zone andthe hydroforming zone between about 300 and about 750 pounds per squareinch gage, effecting both the hydrodesulfurization reaction andhydroforming reaction in the presence of free hydrogen, the mol ratio offree hydrogen to charging stock to the hydrcdesuliurization reactionbeing between about 2:1 and about 9:2 and the mol ratio of free hydrogenVto charging stock to said hydroforming reaction zone being betweenabout 1:1 and about 8:1, indirectly contacting withthehydrodesulfurization reaction a vaporizable heat exchange liquidunder a pressure such that heat exchange liquid is vaporized at atempera-ture suitably related to the temperature of reaction,compressing a major proportion of the vapor thus produced by indirectexchange with said hydrodesulfurization reaction, indirectly contactingwith the hydroforming reaction vapor thus compressed at a pressure suchthat vapor is condensed at a temperature suitably related to thevtemperature of reaction, returning condensate produced by heat exchangewith the hydroforming reaction at a lower pressure for heat exchangewith the hydrodesulfurization reaction, removing a minor proportion ofthe heat exchange vapor from the above heat exchange cycle, condensingthis portion of the heat exchange vapor removed from theheat exchangecycle, and thereafter returningthis .latter portion of the heat exchangevapor to the heat exchange cycle.

11. In an integrated process for the treatment of a hydrocarbon fractioncontaining sulfur to remove sulfur therefrom and to increase thearomatic content thereof involving the successive steps comprisinghydrodesulfurization at a relatively low temperature-and the Vsubsequenthydroforming f the desulfllrzedfeed Stock at a higher temperature, thevimprovement which comprises vaporizing a hydrocarbon feed stockcontaining sulfur and passing same vupward through an elongated'hydrodesulfurization Zone in the presence of a finely-divided catalystat a gas velocity effective to suspend the finely-divided catalyst inthe gaseous reaction mixture and to move finely-divided catalyst inthedirection of ow of the gaseous reaction mixture through saidhydrodesulfurization zone, removing from said hydrodesuliurizaton zonean ellluent containing entrained iinely-divided catalyst and hydrogensulde, removing hydrogen sulfide and finelydivided catalyst from saideilluent of said hydrodesulfurization zone, passing the effluent of saidhydrodesulfurization zone substantially free from hydrogen sulde and inthe vapor state upwardly through the elongated hydroforming zone in thepresence of a finely-divided catalyst at a gas velocity eifective tosuspend the nely-divided catalyst in said gaseous mixture, removing fromsaid hydroforming zone an eiiluent of increased aromatic content,recovering the hydroforming eiiluent as a product of the process,maintaining the hydrodesulfurization zone at a temperature between about'700 and about 925 F. and maintaining the hydroforming zone at atemperature between about 875 and about 950 F., maintaining the pressureof both the hydrodesulfurization zone and the hydroforming zone betweenabout 300 and about 750 pounds per square inch gage, effecting both thehydrodesulfurization reaction and hydroforming reaction in the presenceof free hydrogen, the mol ratio of free hydrogen to charging stock tothe hydrodesulfurization reaction being between about 2:1 and about 9:2and the mol ratio of free hydrogen to charging stock to saidhydroforming reaction zone being between about 1:1 and about 8:1,indirectly contacting with the hydrodesulfuriza- .tion reaction avaporizable heat exchange liquid under a pressure such that heatexchange liquid is vaporized at a temperature suitably related to thetemperature of reaction, compressing vapor thus produced by indirectexchange with said hydrodesulfurization reaction, indirectly contactingwith the hydroforming reaction Vapor thus compressed at a pressure suchthat vapor is condensed at a temperature suitably related to thetemperature of reaction, and returning condensate produced by heatexchange with the hydroforming reaction at a lower pressure for heatexchangewith the hydrodesulfurization reaction.

12. The improved process of claim 1l in which the hydrodesulfurizationreaction is effected in a plurality of successive stages with catalystseparation between stages and in which the Vaporizable heat exchangeliquid is indirectly contacted with the reaction effected in each stage.

13. In an integrated process for the treatment of a hydrocarbon fractioncontaining sulfur to remove sulfur therefrom and to increase thearomatic content thereof involving the successive steps comprisinghydrodesulfurization at a rela- 26;? tively low temperature `and 4thesubsequent hydrofor-rning of the desulfurized feed stock at a highertemperature, the improvement which comprises vaporizing axhydrocarbo'nfeed stock containing sulfur and passing same upward through anelongated hydrodesulfurization Zone in the presence of a Afinely-dividedcatalyst .at a gas Velocity effectiveA to suspend the 'nely-dividedcatalyst in the gaseous reaction mixturey and to move finely-dividedcatalyst in the direction ofA flow of the gaseous reaction mixturethrough said hydrodesulfurization zone, vremoving from saidhydrodesulfurization zone an effluent containing entrainedfinely-divided catalyst and hydrogen sulfide, removing hydrogen suldeand finelydivided catalyst from said effluent of vsaidhydrodesulfurization zone, passing the effluenti of saidhydrodesulfurization zone substantially free from' hydrogen sulfide andin the vapor state upwardly through theA .elongated hydroforming zonevin the presence'of a finely-.divided catalyst at a gas velocityeifective to suspend theiinely-divided catalyst in said gaseous mixtureand to move finely-divided catalyst in the direction of flow of thegaseous mixture through said hydroforming zone, removing from saidhydroforming zone an eiiluent of increased aromatic content andcontaining entrained nely-divided catalyst, separating iinely-dividedcatalyst from the eiiluent of said hydroforming zone, recovering thehydroforming effluent as a product of the process, passing separatedcatalyst from said hydrodesulfurization eluent to said hydroformingreaction zone and passing separated catalyst from said hydroformingeluent to said hydrodesulfurization reaction zone, indirectly contactingwith the hydrodesulfurization reaction a vaporizable heat exchangeliquid under a pressure such that heat exchange liquid is vaporized ata, temperature suitably related to the temperature of reaction,compressing a major proportion of the vapor thus produced by indirectexchange with said hydrodesulfurization reaction, indirectly contactingwith the hydroforming reaction vapor thus compressed at a pressure suchthat Vapor is condensed at a temperature suitably related to thetemperature of reaction, returning condensate produced by heat exchangewith the hydroforming reaction at a lower pressure for heat exchangewith the hydrodesulfurization reaction, removing a minor proportion ofthe heat exchange vapor from the above heat exchange cycle, condensingthis portion of the heat exchange vapor removed from the heat exchangecycle, and thereafter returning this latter portion of the heat exchangevapor to the heat exchange cycle.

14. In an integrated process for the treatment of a hydrocarbon fractioncontaining sulfur to remove sulfur therefrom and to increase thearomatic content thereof involving the successive steps comprisinghydrodesulfurization at a relatively low temperature and the subsequenthydroforming of the desulfurized feed stock at a higher temperature, theimprovement which comprises vaporizing a hydrocarbon feed stockcontaining sulfur and passing same upward through an elongatedhydrodesulfurization zone in the presence of a nely-divided catalyst ata gas velocity effective to suspend the finely-divided catalyst in thegaseous reaction mixture and to move finely-divided catalyst in thedirection of flow of the gaseous reaction mixture through saidhydrodesulfurization zone, removing from said hydrodesulfurization zonean'eilluent con- 27 taining entrained finely-divided catalyst andhydrogen sulfide, removing hydrogen sulfide and :finely-divided catalystfrom said effluent of said hydrodesulfurization zone, passing the-eiuent of said hydrodesulfurization zone substantially free fromhydrogen sulfide and in the vapor state upwardly through the elongatedhydroforming zone in the presence of a finely-divided catalyst at a gasvelocity effective to suspend the finely-divided catalyst in saidgaseous mixture, removing from said hydroforming zone an eiiiuent ofincreased aromatic content, recovering the hydroforming eilluent as aproduct of the process, indirectly contacting with thehydrodesulfurization reaction a Vaporizable heat exchange liquid under apressure such that heat exchange liquid is vaporized at a temperaturesuitably related to the temperature of reaction, compressing vapor thusproduced by indirect exchange with said hydrosulfurization reaction,indirectly contacting with the hydroforming reaction vapor thuscompressed at a pressure such that vapor is condensed at a temperaturesuitably related to the temperature of reaction, and returningcondensate produced by heat exchange With the hydroforrning reaction ata lower pressure for heat exchange With the hydrodesulfurizationreaction.

NORMAN L. DICKINSON.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,139,351 Bejarano Dec. 6, 1938 2,217,703 Pew et al Oct. 15,1940 2,224,014 Dunham et al. Dec. 3, 1940 2,331,433 Simpson et al Oct.12, 1943 2,378,607 Watts June 19, 1945 Y 2,413,312 Cole Dec. 31, 19462,417,308 Lee Mar. 11, 1947 .2,450,724 Grote Oct. 5, 1948 2,483,027 PageNov. 15, 1949 Layng et al. Feb. 21, 1950

1. IN AN INTEGRATED PROCESS FOR EFFECTING CHEMICAL REACTIONS INVOLVINGTHE REACTION STEPS COMPRISING AN EXOTHERMIC REACTION AND AN ENDOTHERMICREACTION, SUCH AS HYDRODESULFURIZATION AND HYDROFORMING, SELECTIVEOXIDATION OF SULFUR AND HYDROFORMING, SYNTHESIS GAS MAKING ANDSYNTHESIS, HYDROGENATION AND HYDROFORMING, SYNTHESIS AND CATALYTICCRACKING OF SYNTHESIS PRODUCT, SYNTHESIS AND REFORMING OF SYNTHESISPRODUCT, AND CHLORINATION OF BENZENE AND HYDROLYSIS OF CHOLOROBENZENE INWHICH REACTANT IS PASSED SUCCESSIVLEY THROUGH THE REACTION STEPS AND INWHICH THE EXOTHERMIC REACTION STEP IS EFFECTED AT A TEMPERATURE NOTHIGHER THAN THE ENDOTHERMIC REACTION STEP AND THE HEAT RELEASED BY THEEXOTHERMIC REACTION STEP IS NOT EQUIVALENT TO THE HEAT REQUIRED BY THEENDOTHERMIC REACTION STEP, THE METHOD FOR SUPPLYING THE REQUIRED HEATFOR THE ENDOTHERMIC REACTION WHICH COMPRISES INDIRECTLY CONTACTING WITHEXOTHERMIC REACTION A VAPORIZABE HEAT EXCHANGE LIQUID UNDER A PRESSURESUCH THAT HEAT EXCHANGE LIQUID IS VAPORIZED AT A TEMPERATURE SUITABLYRELATED TO THE TEMPERATURE OF REACTION, COMPRESSING VAPOR THUS PRODUCEDBY INDIRECT HEAT EXCHANGE WITH SAID EXOTHERMIC REACTION, INDIRECTLYCONTACTING WITH ENDOTHERMIC REACTION VAPOR